<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* .three{
            width: 0;
            height: 0;
            border: 100px solid transparent;
            border-top-color: red;
            border-left: none;
        } */
        .three{
            width: 100px;
            height: 50px;
            background-color: red;
            border-radius: 0 0 100px 100px;
        }
    </style>
</head>
<body>
    <div class="three"></div>
    <script>
        let a = {};
        let b = Symbol("123");
        a[b] = 1;
        a['c'] = 2;
        console.log(a[b]); //1
        console.log(a['c']); //2
        console.log(a['123']); //undefined
    </script>
</body>
</html>